1. Field of the Invention
The present invention relates to a recording thin film magnetic head employed with, for example, a flying magnetic head or the like and, more particularly, to a thin film magnetic head and its manufacturing method wherein a track width restricting groove that fully reaches a lower core layer can be securely and easily formed in an insulating layer interposed between the lower core layer and an upper core layer, and a magnetic pole layer or the like can be properly grown by plating in the groove.
2. Description of the Related Art
FIG. 13 is a partial front view of a conventional thin film magnetic head observed from a surface or an air bearing surface (ABS) opposing a recording medium.
The thin film magnetic head shown in FIG. 13 is a recording inductive head. A reproducing MR head may have been formed at a lower side of the inductive head in the drawing.
Reference numeral 1 shown in FIG. 13 denotes a lower core layer formed of a magnetic material. An insulating layer 9 formed of an insulating material, such as SiO2, is formed on the lower core layer 1.
As shown in FIG. 13, a track width restricting groove 9a is formed in the insulating layer 9. In the track width restricting groove 9a, a lower magnetic pole layer 3 magnetically connected to the lower core layer 1, a gap layer 4, and an upper magnetic pole layer 5 magnetically connected to the upper core layer 6 are formed by plating in this order from a bottom of the groove.
The track width restricting groove 9a is formed from a top surface of the lower core layer 1 to a middle of the insulating layer 9. Slant surfaces 9b and 9b extend from both side upper ends of the groove 9a to a surface 9c of the insulating layer 9 such that an inner width of the groove 9a gradually increases from a track width Tw.
A part of the upper core layer 6 formed on the upper magnetic pole layer 5 so as to be magnetically connected thereto extends away from the lower core layer 1 from tops of the slant surfaces 9b and 9b formed on the insulating layer 9.
FIGS. 14 and 15 illustrate a method for forming the track width restricting groove 9a provided in the insulating layer 9 of the thin film magnetic head shown in FIG. 13.
In a process shown in FIG. 14, the insulating layer 9 composed of an insulating material, such as SiO2, is first formed on the lower core layer 1. Then a resist layer 7 is formed on the insulating layer 9. Thereafter, a predetermined gap 7a is pattern-formed in the resist layer 7 by exposure. A width of the gap 7a is denoted by T1. The width T1 being formed substantially by a track width Tw.
In a step shown in FIG. 15, a portion of the insulating layer 9 that is exposed in the gap 7a provided in the resist layer 7 is etched by reactive ion etching (RIE) to form a track width restricting groove 9a. By the reactive ion etching, the track width restricting groove 9a is formed in a substantially constant width from a surface of the insulating layer 9 to a surface of the lower core layer 1. In this manner, the width of the groove 9a is defined as the track width Tw.
After the track width restricting groove 9a is formed, the slant surfaces 9b and 9b as shown in FIG. 13, for example, are formed. Then the lower magnetic pole layer 3, the gap layer 4, and the upper magnetic pole layer 5 are grown by plating in the track width restricting groove 9a. 
However, according to the conventional structure of the thin film magnetic head and the conventional manufacturing method therefor, when forming the track width restricting groove 9a in the insulating layer 11 by reactive ion etching, it is difficult to form the track width restricting groove 9a that fully reaches the lower core layer 1. A part of the insulating layer 9 tends to remain in a spot indicated by A located between a bottom surface 9d of the track width restricting groove 9a and the lower core layer 1 as shown in FIG. 15.
The part of the insulating layer 9 left in the spot A between the track width restricting groove 9a and the lower core layer 1 causes a slowdown of plating growth of the lower magnetic pole layer 3 and frequently leads to peeling of the plating. The lower magnetic pole layer 3 is formed by plating in the track width restricting groove 9a and continues from the lower core layer 1, Furthermore, the presence of the insulating layer 9 between the lower core layer 1 and the lower magnetic pole layer 3 weakens the magnetic connection between the lower core layer 1 and the lower magnetic pole layer 3, resulting in deteriorated recording characteristics.
The following is a description of a major cause for the failure of forming the track width restricting groove 9a that completely reaches the surface of the lower core layer 1, which causes a part of the insulating layer 9 to be left in the track width restricting groove 9a. The insulating layer 9 is formed of a thick film, making it extremely disadvantageous in etching control. As the insulating layer 9 is etched by the reactive ion etching, undulation develops on the bottom surface 9d of the cut portion, namely, the track width restricting groove 9a as illustrated in FIG. 15. It is difficult to completely remove the insulating layer 9 in the track width restricting groove 9a mainly due to control of etching time. The etching control is even more difficult if the insulating layer 9 is formed of an insulating material, such as SiO2′ that exhibits a high etching rate in the reactive ion etching.